Everyone deserves a hearing no matter what your position in power or how much money you make a year. No matter who you are or the title you have, you are expected to give and receive the same processes that you would if you were in a lower position or with less money.
Senate Majority Leader Mitch McConnell was not wrong in refusing to grant hearings to President Obama's Supreme Court nominee. The Senate has the right to advise and consent. Therefore, by refusing to grant any hearings, the senate advised the president that it did not support his supreme court nominee. Yes, this may have been out of politics, but nonetheless, the senate did not have to grant a hearing.
No, nominations provided by the current president of the United States should not be allowed in the Supreme Court elections of the future president's term. By offering Garland a nomination, Obama is trying to sway the power of the Supreme Court into a more democratic direction, which would benefit him after he leaves the White House. This goes against Trump's political party and the overwhelming republican turnout for the general american population for this term. It is ultimately the decision of the president elect to pick the nominations when he officially takes over office.
Senator McConnell was right in not giving hearings to Barack Obama's Supreme Court pick. He has insisted in a floor speech that the vacancy should be filled by the next president. I think that the next president is not someone who is going to make very good decisions, but it is only fair for him to be the one that thhe deciison is based upon.